Gender Preselection in Farm Animals

Every living being has a set of paired chromosomes, which carry all the genetic material necessary to maintain life and also to propagate new life. All but one pair of chromosomes are called autosomes and carry genes for all the characteristics of the body, such as skin, hair and eye color, mature size, and body characteristics. The remaining pair are called sex chromosomes. They carry the genetic material that specifies gender. One sex chromosome is called X, the other Y. A sperm from the male or an egg from the female contains one of each pair of autosomes; in addition, in mammals the egg always contains an X chromosome, whue the sperm always carries either an X or Y chromosome. When a sperm and egg unite and the sperm carries the Y chromosome, the offspring is male (XY); however, if the sperm carries an X chromosome when it unites with the egg, the resulting offspring is female (XX). In most animals, including humans, the ratio of males to females is 50:50. Because the determination of sex, or gender, takes place when a sperm fertilizes an egg, preselection of gender by selecting the sperm that fertilize eggs must be done before the sperm are used for insemination. In all bird species, including turkeys and chickens, the female determines the sex of offspring. In birds, the sex chromosomes are exactly the same in all sperm, so poultry sperm cannot be manipulated to preselect the sex of offspring.